Fuel oils



United States Patent Office 3,238,026 Patented Mar. 1, 1966 3,238,026 FUEL OILS Femand Noel, Sarnia, Ontario, Canada, assignor to Essa Research and Engineering Company, a corporation of Delaware No Drawing. Filed Sept. 27, 1962, Ser. No. 226,741 4 Claims. (Cl. 4472) The present invention is concerned with improving the characteristics of fuel oils, particularly furnace fuel oils and the like. More particularly, the present invention relates to the preparation of fuel oils having improved characteristics with respect to undesirable mercaptide gel formation and having improved anti-oxidant properties. In particular, the present invention relates to heating oils and diesel fuels, kerosenes, aviation turbojet fuels, and other fuels that are subject to mercaptide gel formation.

'In accordance with the present invention, middle distillates are naturally improved with respect to mercaptide .gel formation and anti-oxidant properties by incorporating therein an effective amount of t-alkylamrnonium talkyldithiocarbamate. The compound is one which is characterized by having the alkyl group highly branched and cotnaining from about 8 to 30, preferably 12 to 22, carbon atoms in the alkyl groups. It is therefore the principal object of the present invention to set forth a mercaptide gelation inhibitor for middle distillates and lighter fuels. In general, these oil boil in the range from 250 to about 750 F. It is a still further object of the present invention to provide heating oils, diesel fuel oils, kerosene and jet fuels with improved antioxidant properties.

Thus, as pointed out heretofore, furnace fuels, particularly those containing small amounts of mercaptans, have a tendency to produce gels which clog various brass fittings through which the oil normally flows as, for example, in the circuit of a heating oil burner. It is known that this gelation is due to a reaction between the mercaptans in the oil and copper from the brass fittings which leads to the formation of oil insoluble copper mercaptides. Copper mercaptides derived from long chain aliphatic mercaptans, e.g. n-dodecanethiol, have an ability to effect gelation of the oil medium. The resulting gel is commonly called mercaptide gel. The present invention, by the use of t-alkylammonium t-alkyldithiocarbamates, prevents the mercaptide gel formation as well as precipitation of the copper mercaptide.

Fuel oils, particularly non-hydrofined furnace fuel oils, also have a tendency to form color and sediment when stored exposed to the air. The formation of sediment is particularly undesirable since it eventually effects plugging of line filters and fine orifices, such as burner nozzles and fuel injectors. The present invention, by use of t-alkylamrnonium t-alkyldithiocarbamates, will inhibit sediment formation in the fuel oils being stored.

The particular t-alkylamrnonium t-alkyldithiocarbamates of the present invention can be synthesized by slowly adding one mole of carbon disulfide to two moles of a tertiary alkyl primary amine, in which the alkyl group is highly branched. The number of carbon atoms in the alkyl group of the primary amine ranges from about 8 to 30 but the preferred range is from about 12 to 22. The reaction temperature is maintained in the range from about 25 C. to 35 C., preferably at a temperature of about 30 C. The following reaction occurs:

2t-RNHz-l-CSz t-RNHii-smaNR-tp The yield is essentially 100% Any excess carbon disulfide is easily removed by evaporation at room temperature under reduced pressure, for example, 200 mm. of Hg. The resulting additive is easily dissolved in suitable solvents such as benzene, xylene, or ethanol, in order to obtain a convenient stock solution which is added to the fuel oil in an appropriate amount.

The amount of t-alkylammonium t-alkyldithiocarbamates used may vary depending upon the particular base oil as, for example, in the range from about 0.0001 to 05 wt. percent, preferably in the range from about 0.005 to 0.1 wt. percent based on the oil.

The important requirement of the t-alkylammonium t-alkyldithiocarbamates is that they be of the following type:

That is, that there be no hydrogen atom on the carbon atom attached directly to the nitrogen. R is any alkyl group which must be branched. A few typical members of this class of compounds are: l,l,3,3-tetramethyl butylammonium, 1,1,3,3-tetramethylbutyldithiocarbamate, and 1,l,3,3,5,5 hexamethylhexylammonium l,1,3,3,5,5-hexamethylhexyldithiocarbamate.

The alkyl groups of the amines used in the synthesis of the additive can be obtained through olefin polymerization using BF The resulting olefin is a complex mixture, which is rather undefinable as olefin tetramers. Consequently, the conversion of these olefin polymers to amines will also afford rather undefinable amine mixtures. Nevertheless, these amines, because of their branchiness, hence increased oil solubility, are preferably used for the synthesis of t-alkylammonium t-alkyldithiocarbamates. Such amines are commercially available and are commonly referred to as Prirnene 8l-R and Primene J.M.T.

Also, the t-alkylammonium t-alkyldithiocarbamates of the present invention should have molecular weights ranging from about 334 to about 950 but preferably from about 446 to about 726.

Typical distillate fuels boiling in the range from 250 to 750 F. to which the present additives may be added are middle distillate heating oils. These fuels are of commercial grade and have typical properties as follows.

Composition:

Straight run gas oil -percent 50 Cat. cracked gas oil do 50 Inspections:

Gravity, API 28.7 ASTM pour, F., no additive +20 Viscosity, centistokes at 100 F. 3.60 Distillation ASTM, F.-

I.B.P 308 10% 466 50% 560 628 =F.B.P 670 In order to further illustrate the invention, a number of tests were conducted as illustrated in the fol-lowing examples.

EXAMPLE 1 Suitable concentrations of oil soluble copper compounds; that is, cupric naphthenate and an aliphatic mercaptan, i.e. n-dodecanethiol, when added to fuel oils will effect a gelation of the oil. The elfect of the talkyldithiocarbamate on this gelation is shown in the following table. In each of these tests a copper naphthenate solution was added to a solution of the mercaptan and talkyl-ammonium t-alkyldithiocarbamate mixture.

Table I.Effect of t-alkylammonium t-alkyldithiocarbamate n gelation (a) Additive structure 1 (b) Each solution contained 0.007 gram mole/liter of cupric naphthenate and 0.028 gram mole/liter of n-dodecanethiol in 25 ml. of a furnace fuel oil.

Additive added mole/ liter: Remarks Nil Rapid gelation of the oil with slight precipitation after 16 hours.

0.0006 No gelation but slight precipitation after 2 hours.

0.00138 Same as above.

0.00422 No gelation and no precipitation.

0.0055 8 Same as above.

0.00965 No gelation but slight turbidity noted.

1A mixture of (312-014 t-alkyl primary amine Was used to synthesize the additive.

From Table I it is evident that in the absence of the additive there is a gelation of the oil. However, in the presence of the additive there is no gelation. When the additive concentration is nearly equal to the copper concentration 0.00422 and 0.007 gram mole/liter respectively, there is no gelation, no precipitation and no observable change. At lower additive concentration there is no gelation but there is precipitation. Addition of larger amounts of additive similarly prevent gelations. However, at 0.00965 mole/liter additive concentration there appeared a slight turbidity but no precipitation.

EXAMPLE 2 An accelerated test was devised to simulate field conditions to demonstrate the effect of the additive on mercapticle gel formation on an actual copper surface.

Copper strips (7X 1.0 cm.) were specially corroded by first polishing with emery cloth, then storing for 24 hours in an ammonia saturated benzene solution. The saturated solution was prepared by shaking benzene with concentrated ammonia solution then separating the henzene layer. The corroded copper strips were then gently wiped, washed in pertoleum ether and air dried before weighing. These copper strips were then suspended in one liter 1:1 blends of lye washed cat. cracked and straight run gas oils. The tests ran at 10 C. for eight hours then room temperature for two days.

Four test solutions of different constituency were made Solution: Composition I Fuel oil blend originally containing 8.4 mg. of mercaptan sulphur per 100 ml. of oil.

II Fuel oil blend with an added 2:221 mixture of n-hexadecyl, n-dodecyl and 2-naphthyl mercaptan. The total mercaptan sulphur concentrations was 114 mg./ 100 ml.

III Same composition as solution II except added 0.01 wt./vol. percent of additive. 1

IV I Same composition as solution II except added 0.1 wt./vol. percent of additive. 1

Additive from reaction of carbon disulphide with a mix ture of Caz-C14 t-alkyl primary amines.

After the aforementioned storage period, the copper strips were gently washed in petroleum ether then air dried. The dried strips were then weighed. The test results are given in Table II.

1 T able II Copper strip Change in weight Remarks from solution of strip (mg) 1.. Nil. No visible change.

II +14.7 A green-yellow gelatinous coating of the strip was formed.

III +109- Same as II.

IV- Nil. Slight darkening of strip.

The above result-s clearly show the antigel-ation propenty of the additive.

EXAMPLE 3 Two 121 blends of lye washed cat. cracked gas oil and straight run gas oil were aerated at 20 C. at the rate of 100 cc./minute. To one oil, 0.01% of t-alkylammonium t-alkyldithiocarbamate was added. The dithiocarbamate used here was made by the reaction of carbon disulphide with a mixture of C C t-alkyl primary amines, by the aforementioned synthesis procedure. During the aerations, the ASTM colors of the solutions were determined. The results are given below:

Table 111 ASTM colors Additive added Nil 0.01%

Aeration time (days):

The results show that the additive slightly improves the color stability of the fuel oil over a definite period of time, after which the color degrades to the level of the uninhibited oil.

EXAMPLE 4 The additive used in these tests was the same as that used in the tests of Example 3. Two oil blends were prepared. Blend A was 4:1 mixture of cat. cracked gas oil and straight run gas oil while Blend B was a 1:1 mixture of the two oils. Each oil used in making the blends had been previously lye washed. Various concentrations of additive were added to the blends, then the resulting solutions were stored in the dark for six weeks in wide mouth open bottles at 43 C. The experimental results are given in Table IV.

1 Starting color was less than 1.0. 2 After 6 weeks storage.

The amount of sediment was determined in each case by filtration through a fine sintered glass filtering crucible, washing the collected sediment with n-heptane, then drying at C. and weighing when dried.

The results show that the additive has a marked effect in decreasing the sediment formation in the furnace fuel oils. The effect is particularly noticeable in the very unstable Blend A, which contains mostly cracked materials.

Thus, the present invention is concerned with reducing the mercaptide gel formation of hydrocarbon compositions, particularly fuel oil compositions. The invention is particularly applicable to those hydrocarbon compositions having mercaptan numbers above about 10, particularly in the range of from about 10 to 100. However, the invention is also effective in reducing the tendency for gel formation even on oils having mercaptan numbers in the range from about 4 to 10. It is preferred that the additive concentration approach the concentration of the copper concentration, as for example that the additive concentration be above 50% of the copper concentration.

What is claimed is:

1. A hydrocarbon fuel oil composition consisting essentially of a major quantity of a hydrocarbon fuel oil containing mercaptans and from 0.0001 to 0.5% by weight based upon the total composition of a t-alkylammonium t-alkyldithiocarbamate having a structural formula as References Cited by the Examiner UNITED STATES PATENTS 2,251,686 8/1941 Musselman et a1. 252402 2,343,393 3/1944 Bergen 252-402 2,912,314 11/1959 Geller et a1. 4472 DANIEL E. WYMAN, Primary Examiner. 

1. A HYDROCARBON FUEL OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR QUANTITY OF A HYDROCARBON FUEL OIL CONTAINING MERCAPTANS AND FROM 0.0001 TO 0.5% BY WEIGHT BASED UPON THE TOTAL COMPOSITION OF A T-ALKYLAMMONIUM T-ALKYLDITHIOCARBAMATE HAVING A STRUCTURAL FORMULA AS FOLLOWS: 